In an experiment, dogs had access to a handle they could pull to release food into a nearby enclosure that contained a familiar dog and nothing else, contained an unfamiliar dog and nothing else, or was empty. The dogs typically released more food to the familiar dog than to the unfamiliar dog. This suggests that dogs are more motivated to help other dogs they know than to help unfamiliar dogs.
The scientist's argument would be most strengthened if it were true that, in the experiment, the dogs with access to the handle tended to release more food when
A. the behavior was being encouraged by a familiar person than when it was being encouraged by an unfamiliar person
B. the enclosure was empty than when it contained an unfamiliar dog
C. an unfamiliar dog in the enclosure was displaying hostility toward them than when an unfamiliar dog in the enclosure appeared friendly
D. a dog in the enclosure appeared uninterested in food already released into the enclosure than when it appeared interested in that food
E. a familiar dog was in the enclosure than when a familiar dog was visible but the enclosure was empty